X-ray photometer



p 9, 1952 c. A. HANSEN, JR 2,610,301

X-RAY PHOTOMETER Filed March 27, 1951 PHASE AMPLIFIER DETECTOR Inventor: Charles AHansen Jn, by a/ 4 M His Attorney about an axis 5 which is perpendicular to the column of X-rays from tube I. A support memher 6 is free to be rotated about a pivot 1 and a; resilient member 8 is fastened. at one end tosupport 6 and at the other end' to crystal 4.

An eccentric 9 is rotated by the shaft of a synchronous electric motor H] which is supplied from a source having the same frequency'as the source supplying X-ray tube l and is from the same source.

A bar magnet I] is mounted adjustably on the shaft. of motor In and normal thereto. The mounting of magnet H is adjustable so that the angular position of magnet ll relative to the rotor of motor I0 may be varied. A C-shaped ferro-magnetic core I2, having a coil l3 wound thereon, is located with respect. to magnet H such that an alternating current is induced in coil l3. This current has a frequency equal to the frequency of rotation of the shaft of motor It.

A scale 14 is positioned opposite an indicator [5 on support 6 to indicate the relative position of support 6 and the parts mounted thereon with respect to collimator 3. A fluorescent screen 16 is mounted on support 6 .to intercept the monochromatic X-rays refracted from crystal 4. Screen [6 transforms the X-ray energy incident thereon to lower" energy light rays which determine the current output of a phototube type of transducer IT. A cone-shaped light collector 18 increases the efficiency of the system, as is well known in the art. The output of phototube H is supplied to amplifier I9 and then to a phase detector 20. Phase detector 20 is also supplied with a synchronizing signal from coil .13. In the phase detector the signals from phototube I! are 1 combined with the synchronizing signals from coil 13 to produce .an output signal which is indicatiye of the difference in magnitude of, succeeding Xeray pulses.

A suitable phase detector circuitfor use in this H invention is illustratedand described in the article entitled .X-Ray Photometer by P. C. Michel and T. A. Rich appearing in the February 1947 issue of General Electric Review. of the article illustrates the circuit, entitled amplifier and phase detector circuit. vIn the description, the amplifier and phase detector portions thereof are treated separately. The term phase detector 20 as employed herein, however, includes both portions. A conventional ammeter 2| is connected tov be supplied with the output of phase detector 20. Although an am meter has been shown, it will be understood that any other visualindicator of current may be employed or perhaps the output of the phase detector may be used to energize a control circuit.

In operation, a schematically represented sample S to be tested is placed between crystal 4 and fluorescent screen I6 andmotor leis-connected to rotate at a frequency half of that of the voltage supplied toX-ray tube I. Eccentric 9 thus causes. crystal 4 to vibrate about a mean position at half the frequency of the dent thereto- Asynchronizing signal having the preferably supplied 1 Fig.5

X-ray. pulsesv inci-.

same frequency as that of motor In is supplied from the coil 13 of the magnet assembly to the phase detector. This pick-up signal is used rather than a signal direct from the line to allow adjustment for phase differences by shifting the magnet H on the motor shaft. Support 6 is slowly rotated about pivot I and the angle of incidence between the X-raycolumnand the mean position of crystal 4 is indicated on dial l4. When the wave length of the monochromatized X-rays penetrating the sample reaches a K-band, succeeding X-ray pulses impinging on screen l6 have greatly differing magnitudes, which is indicated by meter 2 I. At this time, the position of pointer i 5 on dial-l4 gives an indication of the monochromatized wave length refracted by crystal 4 and, hence, of the particular element present in the sample. The magnitude of the current change in meter 2| is indicative of the relative amount of the particular element in the sample.

In some cases, the magnitude ofthe-K absorption edge is aif'ected by the presence ;of other elements, which, of course, meansthe magnitude of meter signal is affected. However, the positive change in output, which indicatesthe element, will be present under any circum stances, and quantitative analysis may be had withyalmost any sample by the use of, empirical means.

Modifications of ;this invention will. occur to those skilled in the art audit is desired to be understood, therefore, that this invention. is not to be limited to the particular embodiment disclosed, but thatthe appended claimsciire meant to cover all the modifications-which are-within the spirit and scopeof, this invention;

What I claimas new anddesireto secure by- Letters Patent of the United States; is:

1 An X-ray photometer. comprising. a,-sourceof pulsed collimatedX-rays, monochromatizingmeans positioned to intercept saidX-rays includ-v ing a crystal pivotally mounted on an axisperpendicular to the longitudinal axis ofthe column of X-rays, said crystal being mounted such that the average angular position thereof. maybe gradually varied; a motor .for :oscillating said crystal a determinable amount aboutsaidpivotal axis; means indicating the mean angular -posi-- tion of said crystal; a fluorescent screen-positioned to intercept the column-- of X-rays refracted by. said crystal; transducingmeans posi tioned to be energized by light fromsaid screen and-to transform the energy of said light into electric energy, and electric means connected to indicate the difference in the magnitudes of the output of said transducing means at -the opposite maximum excursions of saidcrystal through any mean angle.

2. An X-ray photometer --comprising a discharge device radiating X-rays, asource ofa1- ternating voltage connected to supply energy to said device; a collimator located inspaced rela tionship with. said device to-collimate a portion of the X-ray energy radiated therefrom; a monochromatizing crystal-positionedon a rotatable support to monochromatizethe-column-of X- rays, said crystal being-pivotally mounted on an axis perpendicular to the longitudinal axis of said column of X-rays; a wobble motonconnected to' vibrate said crystal about the pivot-axis, the fre quency of vibration being half the frequency of said source of alternatingvoltagmmeans'indicating the mean angular position of-said crystal; a fluorescent screen positioned --to-intercept the column of monochromatizedX-rays refracted by} said crystal; .transducing means positioned to be 5 energized by light from said screen and to transform the energy of said light into electric energy; and electric means connected to be supplied with the output of said transducer and a synchronizing signal controlled by said motor to indicate the difference in the magnitudes of the output of said transducing means at the opposite maximum excursions of said crystal through any mean angle. 1 CHARLES A. HANSEN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Number Name Date 2,452,045 Friedman Oct. 26, 1948 2,469,206 Rich May a, 1949 5 2,474,835 Friedman July 5, 1949 2,539,196 Marshall Jan. 3, 1951 OTHER REFERENCES X-Ray Photometer by T. C. Michel et al., G. E. 10 Review, pp. 45-48, Feb. 1947. 

